The present invention relates to an arrangement for fixing or mounting a power-operated clamping device for workpieces or tools on a hollow machinetool arbor or spindle in which is disposed a spreader or securing rod that is adapted to be coupled with a drive member of the respectively mounted clamping device, and that is adapted to be actuated by a hydraulic or pressurized cylinder secured to a rear end of the spindle, with a front end of the spindle being provided with a flange to which is secured an intermediate ring to which a body of the clamping device is adapted to be secured via at least two securing bolts or pins, with the clamping device being centered on the intermediate ring via central conical surface means.
An arrangement of this general type for mounting a power-operated clamping device on the front end of a hollow machine-tool spindle is disclosed, for example, in German Patent No. 33 28 291. With this known arrangement, radially oriented securing pins are mounted in the intermediate ring that is secured to the flange of the spindle. Draw-in or tightening surfaces of the securing pins engage in an annular groove that is formed in a flange ring, which in turn is secured to the body of the clamping device. To center this flange ring relative to the intermediate ring that is secured to the flange of the spindle, central conical surfaces are formed both on the flange ring and on the intermediate ring. Actuation of the securing pins is effected by pistons that are connected to the securing pins, with pressure medium being supplied to the pistons via lines that extend in the spindle.
Furthermore, in order to provide for an automatic rapid exchange of clamping devices on machine-tool spindles it is necessary to be able to rapidly detachably couple the drive member of the respectively mounted clamping device with the securing rod that is disposed in the hollow machine-tool spindle, so that the respectively mounted clamping device can be actuated by the pressure medium cylinder that is secured to the rear end of the spindle. With the embodiment known from the aforementioned German Patent No. 33 28 291, this coupling is effected via a coupling head that is disposed on the securing rod and that has distributed over the periphery radially outwardly directed coupling cams that cooperate with radially inwardly projecting coupling projections of a coupling adapter that is in turn disposed on the drive member of the respectfully mounted clamping device. In a rotational position of the securing rod that corresponds to the uncoupled state, the coupling head, with its coupling cams, can be introduced axially into the coupling adapter between the coupling projections. By rotating the securing rod the coupling cams pass behind the coupling projections, so that in this position the drive member of the clamping device is positively connected with the securing rod that can be actuated by the pressure medium cylinder. In order to rotate the securing rod between the two end positions, namely the uncoupling position on the one hand and the coupling stage on the other hand, in addition to the axial piston cylinder that actuates the drive member of the mounted clamping device, the heretofore known arrangement is provided with a rotary piston cylinder that is disposed at the rear end of the machine-tool spindle.
The known arrangement of the aforementioned German Patent No. 33 28 291 has various drawbacks. On the one hand, the rotary piston cylinder that is necessary for the coupling process between the securing rod and the drive member of the clamping device is technically complicated and represents an additional loading of the machine-tool spindle. In addition, this rotary piston cylinder precludes an overall hollow configuration for the securing rod, so that no rod-like workpieces can be supplied through the machine-tool spindle to the respectively mounted clamping device. Furthermore, due to the radial orientation of the securing pins, a large bulky arrangement that extends out quite far radially results not only for the intermediate ring but also in particular for the flange ring that provides the annular groove for the securing pins, so that this heretofore known construction is very heavy and has a high flywheel mass.
A further clamping arrangement disclosed in German Offenlegungsschrift 30 45 536 has similar drawbacks. This arrangement also has radially oriented securing pins for securing the body of the clamping device on the spindle flange. However, with this arrangement the interlocking between the drive member of the clamping device and the securing rod that extends in the spindle is effected via balls that are held in recesses of the securing rod and that can be actuated via an additional actuation rod that is guided in the hollow securing rod in such a way that they enter in corresponding, spherical segment-like recesses of a coupling member that is connected with the drive member.
With the arrangement disclosed in the aforementioned German Offenlegungsschrift 30 45 536, not only for the actuation of the radial securing pins via wedge surfaces, but also for the axial coupling movement of the actuating rods, in each case an additional adjusting cylinder is provided at the rear end of the machine-tool spindle, so that altogether three such axial piston cylinders must be used, the tubular actuating rods of which must collectively be disposed in the hollow machine-tool spindle. If there is a disruption in the pressure medium system, the danger exists that the clamping device will come loose from the spindle flange, so that despite a high structural expense, an only inadequate operational reliability is provided. A very similar construction, which has the same drawbacks, is disclosed in German Offenlegungsschrift 30 45 537.
Finally, German Offenlegungsschrift 34 10 670 discloses a further construction where a clamping device body, which is again provided with a flange ring, is fixedly connected via a self-centering radial tooth construction with an intermediate ring that is secured to the machine-tool spindle. The securing of the flange ring on the intermediate ring is effected via a plurality of clamping segments that couple a collar of the intermediate ring in a clamp-like manner with a connecting sleeve, which in turn is connected with the piston rod of one of the axial piston cylinders. An appropriate coupling between segments is effected between the front end of the securing rod and the drive member of the respectively mounted clamping device. In addition to a high expense for construction and the impossibility of providing a continuous bore for the supply of rod-like workpieces, this heretofore known construction has the drawback that both interlocking operations are a function of the position of the respective piston, so that if problems occur in the pressure medium system, not only a loosening but even a detachment of connections can occur.
Starting with the previously described arrangement of German Patent 33 28 291, it is an object of the present invention to embody such a mounting arrangement in such a way that via a straightforward construction and with small overall size, a reliable coupling is effected not only between the body of the clamping device and the spindle flange but also between the drive member and the securing rod, with this being accomplished without the need for an additional actuating cylinder at the rear end of the machine-tool spindle, whereby the possibility should be provided for being able to supply rod-like workpieces to a mounted clamping device through the machine-tool spindle.